(1) Field of the Invention
The present invention pertains to a furnace heat exchanger seal that employs a silicone sponge pad and the method of employing the pad in sealing connections between furnace heat exchanger component parts.
(2) Description of the Related Art
In the construction of furnace heat exchangers, the heat exchanger cell or combustion chamber is typically connected to a mounting plate. The connection is made with an aperture in the plate adjoining the burner and flue gas opening in the heat exchanger cell. To prevent flue gases from mixing with the heated air circulated over the heat exchanger cell exterior, the connection of the mounting plate aperture and heat exchanger cell opening must be sealed air tight. The present practice of sealing heat exchanger seams involves applying a bead of a wet sealant around the plate aperture prior to insertion of a flange surrounding the heat exchanger opening through the aperture and bending the flange outward around the aperture in connecting the heat exchanger to the mounting plate.
In some applications, the wet sealant paste or gum is applied at points adjacent the mounting plate aperture that correspond to positions of seams in the heat exchanger when the heat exchanger is joined to the mounting plate. The wet sealant applied at these points on the mounting plate seals any openings between the heat exchanger seams and the mounting plate once the heat exchanger is assembled to the mounting plate.
Each of the above described prior art methods of sealing the connections between furnace mounting plates and heat exchanger cells are disadvantaged in that the sealant must be applied just prior to the connection of a heat exchanger cell to a mounting plate. Sealants, such as wet silicone, set-up after a short period of time so the heat exchanger cell and mounting plate must be assembled together shortly after application of the wet sealant. This prevents furnace component parts from being stockpiled with the sealant already applied to the parts because the sealant will set-up before the parts are used in assembling a furnace. The requirement that the sealant be applied to the parts just prior to their assembly adds an additional step in the assembly of furnace heat exchangers to mounting plates. The additional assembly step results in an increase in the costs involved in manufacturing furnace heat exchanger assemblies.
In efforts to reduce the costs involved in constructing furnace heat exchanger assemblies, the sealant application process has been automated. However, because the typical wet sealant will set up after a short period of time, the automated application of sealant to the parts of a heat exchanger assembly must still take place just prior to the assembly of the parts. Moreover, the automated process of applying sealant at times applies more sealant than is necessary for the seal, thereby wasting sealant and increasing production costs. Too much sealant applied to the connection of a furnace heat exchanger wall and a mounting plate, whether manually or by automation, will also often cause sealant to stick to the flange bending tools employed in forming the connection. This results in the added expense of the down time of the tool while it is cleaned or repaired.